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Thread: Angle of attack

  1. #1

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    Angle of attack

    Aircraft Spruce sells three different AOA's.
    One uses a probe under the wing, one measures the difference in pressure above and below the wing, the third uses a vane in the airflow to measure angle.
    Does any one have experience with them?
    ie:
    Ease of installation
    Ease of setup
    How suceptable to damage
    Do they allow accurately for flap selection

    I assume the accuracy of each is acceptable

    Most large a/c use the vane type, is it inherently better?

    Ray

  2. #2
    steveinindy's Avatar
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    I have never seen a head to head comparison between the types or different manufacturers. That said, my preference has always leaned towards the vane type because of the idea that if it is good enough for the military or airlines then it's good enough for the slow little airplanes most of us fly.
    Unfortunately in science what you believe is irrelevant.

    "I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.



  3. #3

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    Quote Originally Posted by raytoews View Post
    Aircraft Spruce sells three different AOA's.
    One uses a probe under the wing, one measures the difference in pressure above and below the wing, the third uses a vane in the airflow to measure angle.
    Does any one have experience with them?
    ie:
    Ease of installation
    Ease of setup
    How suceptable to damage
    Do they allow accurately for flap selection

    I assume the accuracy of each is acceptable

    Most large a/c use the vane type, is it inherently better?

    Ray
    I only have experience with the AFS AOA unit. Here is a link to a presentation that may provide some additional insight.

    http://www.advanced-flight-systems.c...A%20slides.ppt

    In my installation, both the EFIS and AOA are aware of the current flap setting.
    --
    Bob Leffler
    RV-10 Flying
    www.mykitlog.com/rleffler

  4. #4
    Quote Originally Posted by raytoews View Post
    Aircraft Spruce sells three different AOA's.
    One uses a probe under the wing, one measures the difference in pressure above and below the wing, the third uses a vane in the airflow to measure angle.
    Does any one have experience with them?
    ie:
    Ease of installation
    Ease of setup
    How suceptable to damage
    Do they allow accurately for flap selection

    I assume the accuracy of each is acceptable

    Most large a/c use the vane type, is it inherently better?

    Ray
    I have been flying an LRI angle-of-attack indicator in the RV-6 for ten years. I consider it one of the most important instruments in the panel. You can read my article about my LRI installation here:

    http://thervjournal.com/liftreserve.htm

    When the Dynon D-10A was installed in my panel I replumbed the AOA lines to also feed the Dynon AOA indicator via the LRI probe. This works perfectly which retains the mechanical LRI indicator but adds the Dynon audible warning.

    I built an LRI for my Legal Eagle and it works great in the low-n-slow corner of the performance envelope, too. The LRI is my primary take-off and landing instrument in both the RV-6 and Legal Eagle XL and is the key to safely achieving high-performance landings.

    I highly recommended AOA regardless of which system is used. The vane type system would be my least preferred method since it relies on a mechanical sender, is prone to damage.......and looks ugly. Both the probe and port systems work very nicely.
    Last edited by Sam Buchanan; 12-15-2012 at 06:39 PM.
    Sam Buchanan
    EAA Technical Counselor
    The RV Journal RV-6 build log
    Legal Eagle XL build log
    APRS track

  5. #5
    iFLYblog's Avatar
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    I really need to get an AOA. I had plans to when I built the airplane, but talked myself out of it. Sam, you make a great argument for it.
    Brent Owens
    RV-8 'Contrary Mary' - Flying
    EAA 9 Vice President / Tech Counselor / Flight Advisor
    www.iflyblog.com



  6. #6

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    Brent,

    The good news is all you need is the AFS AOA wing kit to display on your EFIS. I'm assuming that you have the 3500 and not the 2500. It's a pretty simple mod to install. You can reach everything from the wing tips and all you have to do then is pull the tubing through the wing into the cockpit. The AFS provided tubing is much smaller than the 1/4" tubing used for the pitot.

    Some folks do prefer the AOA display mounted on the glareshield, which I think is better too, since you keep you head out of the cockpit during landing. Budget forced me to settle for the one on the EFIS. But then I can always add the glareshield mount display later as budget permits.

    bob
    --
    Bob Leffler
    RV-10 Flying
    www.mykitlog.com/rleffler

  7. #7
    Anymouse's Avatar
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    I had the AFS AOA installed prior to first flight. It's worked flawlessly since then. A few years later I got their EFIS. I opted to keep the original AOA display, rather than pay the extra to have it displayed on the EFIS. I'm glad I did it that way. The display on the EFIS is much smaller and can get lost with all the other info that's being displayed.

    JMNSHO
    I'll come up with something profound

  8. #8

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    This might be a very good product test for AVIATION CONSUMER to do. It would take instalation and therefore a lot more work and expense than many of their others tests.
    Maybe one of you guys who know or use A C will suggest/request it from them.

    I have long thought about having one of the AOA systems. A story is that Orville Wright said that it should be used after his ride on a big Connie or DC-4 type when he was gettin along in years.

    The biggest reason that I have not installed the AOA is having to cut into the wing, and also shortage of panel space for the indicator. I don't have any EFIS in my plane and don't want one, but if I did have an AOA, I would like to have it stand out and not be buried in another display if I was going to be using for a critical moment like landing.

    My guess, and nothing much to base this on , is that once you start using an AOA you probably find that is and the airspeed indicator are pretty much in agreement. By that I mean that if you do a short field slow landing and come in on the margin at the bottom of the color arc on the AOA, then you will be at the speed that you would use anyway on the airpseed indicator for such a landing. Thus one comfirms the other.

    I think I guess this is true is because most airplanes, not counting some jet, but most normal piston type airplanes have and do use an airpspeed indicator, and have not gone to AOAs. Now maybe that is also becaue the normal airspeed indicator is cheaper than the AOA system, even if not really better.

    Obviously we can and have flown for a century or so without having AOAs in most planes an it works ok.
    Last edited by Bill Greenwood; 12-18-2012 at 02:18 PM.

  9. #9

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    Quote Originally Posted by Bill Greenwood View Post
    The biggest reason that I have not installed the AOA is having to cut into the wing, and also shortage of panel space for the indicator. I don't have any EFIS in my plane and don't want one, but if I did have an AOA, I would like to have it stand out and not be buried in another display if I was going to be using for a critical moment like landing.
    Bill,

    Not all solutions require cutting into the wings and/or panel space.

    The AFS AOA only requires a few holes to be drilled into the wing. Two are for mounting screws and the third, which I believe is a 3/64th is for the opening for the AOA. They have a monitor that is about the size of your thumb and can sit on top of your glare shield. 12v to the module installed behind your panel and run the two small tubes out to the wing and you're done. Pretty straight forward to install if you have aluminum wings.

    bob
    --
    Bob Leffler
    RV-10 Flying
    www.mykitlog.com/rleffler

  10. #10
    Anymouse's Avatar
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    Quote Originally Posted by Bill Greenwood View Post
    My guess, and nothing much to base this on , is that once you start using an AOA you probably find that is and the airspeed indicator are pretty much in agreement. By that I mean that if you do a short field slow landing and come in on the margin at the bottom of the color arc on the AOA, then you will be at the speed that you would use anyway on the airpseed indicator for such a landing. Thus one comfirms the other.
    Keep in mind that an AOA is also a stall warning device.
    I'll come up with something profound

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